In the current industrial production area, there are many flow test situations. Flow test methods mainly focus on conventional methods such as turbine flow test, vortex flow test, pressure-type flow test by using a Venturi tube, and electromagnetic flow test. With the development of the fiber optical sensing technology and the diversity of flow test environments, in order to implement flow tests in harsh environments such as an antimagnetic environment, an anti-explosion environment or a high-temperature and high-pressure environment, there have been many researches on flow test methods based on the fiber optical sensing technology at present in consideration of the good anti-magnetism, anti-explosion and anti-interference performance of the fiber optical sensing methods.
Zhang Wentao et al. disclosed a flowmeter based on fiber optical dynamometry (Chinese patent application No. 201210464779.3), wherein fluid in a main pipe is guided to a branched test pipe through a diversion structure at a certain flow rate, and then transferred to a fiber optical sensing structure through a dynamometry diaphragm device for flow tests. Li Tianshi et al. disclosed an underground fiber optical flow sensor in an oil field (Chinese patent application No. 201310174087.X), which is packaged by a high-pressure-resistant diaphragm made of stainless steel and realizes flow tests by testing the path difference caused by pressure.
Hua Xia et al. disclosed a fiber optical sensing system in a harsh environment (Patent No. US2011/0170823A1), wherein an optical sensor consists of a periodic or quasiperiodic microcrystalline or silicon dioxide tetrahedral structure and a cladding layer adapted to a fiber optical core. Mikko J et al. disclosed a fiber optical system for monitoring flow (Patent No. US2014/0260588A1), wherein a sensor device is disposed at a head end of a drill rod, and a small flow test is realized by a double-fiber bragg grating.
Although the fiber bragg grating (hereinafter referred to as FBG) sensing technology may realize flow tests, it will be cross impacted by temperature due to high temperature sensitivity. Therefore, how to solve the problems in the existing fiber optical flow test technologies, such as the temperature cross-sensitivity impact on flow tests in high-temperature and high-pressure environments, has become an important research interests in the current fiber optical flow test technology.